There are several common factors associated with hearing loss in Tucson.
Aging, noise exposure, disease and ototoxic medications can all contribute to hearing impairment.
Understanding the mechanisms behind hearing loss is a necessary step in managing the condition – and possibly even coming up with ways to prevent it.
Ototoxicity and Medications
More than 200 drugs have been classified as ototoxic – that is, they have the ability to damage hearing.
The most common medications to have an adverse effect on hearing include quinine, chemotherapy drugs, loop diuretics, nonsteroidal anti-inflammatory drugs (NSAIDs) and aminoglycoside antibiotics such as gentamicin.
These drugs can all lead to temporary or permanent hearing loss and tinnitus.
Aminoglycosides are known as broad-spectrum antibiotics; rather than targeting specific microbes, as narrow-spectrum antibiotics are designed to do, these work on a wide range of bacteria.
Gentamicin and other aminoglycosides are often used to treat infants in neonatal intensive care units; infections in premature babies often prove deadly before doctors can determine which bacteria are at fault.
While broad-spectrum antibiotics are successful in treating infection, the downside is their ability to damage hearing.
Infants prescribed these drugs are six times more likely to develop hearing loss compared to healthy babies with normal hearing.
Researchers from Creighton University in Nebraska, led by Peter Steyger, wanted to examine the link between antibiotics and hearing impairment.
Doctors have long understood that these drugs cause hearing damage, but haven’t known why.
Steyger and his team tested gentamicin on mice in order to measure its effects.
They were able to determine that inflammation associated with infection caused ion channels in the tiny hair cells of the cochlea to become more permeable to the antibiotics, allowing more of the drug to absorb into the inner ear.
This made the mice more susceptible to the medication’s toxic properties.
One protein– TRPV1 – had an especially profound effect on the ion channels and helped gentamicin enter the sensory cells when inflammation was occurring.
Researchers bred mice without the TRPV1 protein and found that the genetically-altered rodents were protected against hearing loss even when body-wide inflammation was occurring.
These findings are a cautionary tale for doctors; they demonstrate that narrow-spectrum antibiotics should be used to treat infections whenever possible, in order to limit the chances of hearing loss from occurring in patients with body-wide infections.
This isn’t always possible, of course; there are cases in which aminoglycosides are the only viable treatment option.
Signs of Hearing Loss
Health care providers must monitor these patients carefully for signs of hearing loss and treat the condition as soon as possible in order to improve their long-term outcome.
“This is especially important in children learning to listen and speak,” Steyger explains, “where delay in identifying hearing loss has lifelong consequences including delayed acquisition of spoken language, less academic success and reduced income.”
His research team is urging the development of new techniques that would allow doctors to identify bacteria causing infection more quickly to reduce the use of potentially damaging broad-spectrum antibiotics.
For more information on the link between antibiotics and hearing, talk to your Tucson audiologist.